Sema: Use VarDecl::isLayoutExposedToClients() when checking if @_spi attribute is allowed

We need to prohibit 'lazy' properties and property wrappers from
being declared @_spi inside of a @Frozen struct. Making them SPI
doesn't make sense, because these properties will be omitted from the
module interface and not taken into account when clients manipulate
values of this type.

Author: slavapestov

lib/Sema/TypeCheckAttr.cpp

@@ -967,14 +967,15 @@ void AttributeChecker::visitSPIAccessControlAttr(SPIAccessControlAttr *attr) {
     }
 
     // Forbid stored properties marked SPI in frozen types.
-    if (auto property = dyn_cast<AbstractStorageDecl>(VD))
-      if (auto DC = dyn_cast<NominalTypeDecl>(D->getDeclContext()))
-        if (property->hasStorage() &&
-            !DC->isFormallyResilient() &&
-            !DC->isSPI())
+    if (auto property = dyn_cast<VarDecl>(VD)) {
+      if (auto NTD = dyn_cast<NominalTypeDecl>(D->getDeclContext())) {
+        if (property->isLayoutExposedToClients() && !NTD->isSPI()) {
           diagnoseAndRemoveAttr(attr,
                                 diag::spi_attribute_on_frozen_stored_properties,
                                 VD->getName());
+        }
+      }
+    }
   }
 }
 

test/SPI/spi_members.swift

@@ -9,7 +9,7 @@ public struct Wrapper<T> {
 
 @_spi(Foo)
 public class Bar {
-  // expected-note@-1 11{{type declared here}}
+  // expected-note@-1 12{{type declared here}}
 
   public init() {}
 }
@@ -42,9 +42,19 @@ public struct Resilient {
   // expected-error@-1 {{stored property 'storedProperty2' cannot be declared '@_spi' in a '@frozen' struct}}
 
   @_spi(Foo) public lazy var lazyProperty1 = Bar()
+  // expected-error@-1 {{stored property 'lazyProperty1' cannot be declared '@_spi' in a '@frozen' struct}}
+
   @_spi(Foo) public lazy var lazyProperty2: Bar = Bar()
+  // expected-error@-1 {{cannot use class 'Bar' here; it is SPI}}
+  // expected-error@-2 {{stored property 'lazyProperty2' cannot be declared '@_spi' in a '@frozen' struct}}
+  // expected-error@-3 {{class 'Bar' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
+  // expected-error@-4 {{initializer 'init()' cannot be used in a property initializer in a '@frozen' type because it is SPI}}
+
   @_spi(Foo) @Wrapper public var wrappedProperty1: Bar
+  // expected-error@-1 {{stored property 'wrappedProperty1' cannot be declared '@_spi' in a '@frozen' struct}}
+
   @_spi(Foo) @Wrapper public var wrappedProperty2 = Bar()
+  // expected-error@-1 {{stored property 'wrappedProperty2' cannot be declared '@_spi' in a '@frozen' struct}}
 }
 
 @frozen public struct Bad {